Refer to the figure below. Growing 1,000 bushels of wheat and no bushels of corn each year is:

Refer to the figure below. Growing 1,000 bushels of wheat and no bushels of corn each year is:
A.efficient and attainable.
B.efficient but unattainable.
C.inefficient and unattainable.
D.inefficient but attainable.
正确答案：efficient and attainable.